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NEUROSCIENCE OF PSYCHOACTIVE SUBSTANCE USE AND DEPENDENCE

psychosocial care and low doses of the neuroleptic drugs that are used to treat
schizophrenia (McGorry, Yung & Phillips, 2001). Studies in Australia and the
USA have shown that it is possible, using standardized criteria, to identify a
group of young people who have a high risk (30–40%) of developing
schizophrenia in the ensuing 6 to 12 months (McGlashan, 2001; McGorry, Yung
& Phillips, 2001). A number of quasi-experiments and randomized controlled
trials suggest that the combined intervention reduces the rate at which
schizophrenia occurs and reduces its severity (McGorry, Yung & Phillips, 2001).
Similar trials can be foreseen for substance dependence, once research clarifies
the risk and protective factors, genetic predisposition, and treatment options.
Critics of these studies have raised a number of ethical issues (Cornblatt,
Lencz & Kane, 2001; DeGrazia, 2001). These include the fact that there is a
high false positive rate: 60% of those who are identified as being at risk of
developing schizophrenia do not develop the disorder. This can also be seen
to apply to the development of substance dependence. There is also the
potential for stigmatization and discrimination against those who are
identified as being at risk. Even if there is no discrimination, there is the
possibility that there will be adverse effects on individuals of being labelled
as at risk. There is also concern about the capacity of children and adolescents
to consent to participate in such studies, and doubts about the acceptability
of using proxy parental consent. Long-term preventive treatment with drugs
may have health consequences. McGorry, Yung & Phillips (2001) have
countered, with respect to schizophrenia, that the potential benefits (the
prevention of schizophrenia and early treatment of cases that do occur)
outweigh the potential risks of neuroleptic medication and stigmatization,
both of which they suggest (on the basis of controlled studies) have been
exaggerated.
Analogous approaches to early interventions could be taken for substance
dependence, although to date no trials have been explicitly undertaken with
the aim of using pharmacotherapies as preventive interventions for substance
dependence. It is likely that many of the same ethical issues would arise.
Psychostimulant drugs, such as methylphenidate and dexamphetamine, have
been used to treat children and adolescents with attention deficit
hyperactivity disorder (ADHD), an intervention that is controversial (Levy,
1997). Since ADHD in combination with conduct disorders increases the risks
of developing substance use disorders (Lynskey & Hall, 2001), and
psychostimulant drugs reduce symptoms of ADHD (Swanson et al., 1998),
an unintended by-product of psychostimulant medication may be the
prevention of substance use disorders. However, no one has so far argued for
the use of psychostimulant medication to prevent substance dependence,
and it is unlikely that anyone would do so. Public concern about the long-
term use of stimulant drugs to treat ADHD suggests that any such proposal
will be opposed and support for the chronic use of drugs in late childhood or
adolescence to prevent the development of substance dependence would
seem to be even less likely.

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